Possible Cancer Risk Fuels Byetta, Januvia Debate

A controversy has erupted around Byetta and Januvia, drugs used to treat type 2 diabetes. Some recent research indicates that medications like Byetta and Januvia may raise risks for pancreatic cancer and pancreatitis, but manufacturers of the drugs insist they are safe.

Both Byetta and Januvia lower blood sugar levels for diabetics by promoting the action of the hormone glucagon-like peptide 1 (GLP-1) in the gut. A study published over the summer by the journal Gastroenterology found that use of either Byetta or Januvia was associated with a 6-fold increased risk of pancreatitis as compared with other therapies. The same study also found that the event rate for pancreatic cancer was 2.9-fold greater in patients treated with Byetta compared to other therapies, and 2.7-fold greater among patients taking Januvia.

The Gastroenterology study was based on an analysis of reports made to the U.S. Food & Drug Administration (FDA) Adverse Event Reporting Database between 2004 and 2009. The findings do not prove that either drugs cause cancer, but did raise concerns that they and other GLP-1 therapies, including Victoza, could raise cancer risks.

The issue took center stage last week, during a debate at the European Association for the Study of Diabetes meeting.

“The data we have so far makes the question sufficiently robust that it has to be answered,” Peter Butler, a researcher at the University of California at Los Angeles and author of the Gastroenterology study, said in an interview with Bloomberg News. “Hopefully this debate will raise the awareness of the scientific community, so that people will be motivated to join in the research.”

During the debate, Butler’s study was criticized by Novo Nordisk, maker of Victoza, which according to Bloomberg, asserted that the FDA’s voluntary reporting system can’t be used to calculate the incidence of side effects.

According to Bloomberg, Butler’s study was also disputed by a German researcher. “The bulk of findings tends to speak against such an association,” Michael Nauck, head of the Diabeteszentrum Bad Lauterberg in Harz, Germany, said in an interview. “There is no general agreement.”

During the debate, Nauck said his own analysis of FDA Adverse Events “using very, very similar methods” failed to establish a link between GLP-1 therapies and cancer, but may show the drugs protect against certain other forms of cancer, such as prostate tumors.

According to Bloomberg, both Butler and Nauck did agree that prospective randomized clinical trials are needed to conclusively show whether GLP-1 therapies carry an increased risk of cancer.

The uncertainty surrounding the potential side effects of GLP-1 therapies like Byetta and Januvia prompted some at the meeting to call for limitations on their use.

“I am not sure we are totally aware what happens with these drugs. I only prescribe them when it’s absolutely necessary. Otherwise I avoid them,” Gerard Guillain, an endocrinologist in Nice, France, said, according to Bloomberg.